1. Field of the Invention
The present invention relates to a scanner apparatus suitably used for an image scanner, a copying machine, a facsimile, and a multifunction peripheral.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 2009-253327 discusses a flat-bed type scanner apparatus that includes a line sensor unit (contact image sensor (CIS) unit) configured to scan and move with respect to a document placed on a platen. In this apparatus, the line sensor unit is biased to a glass plate of the platen by a coil spring. In both ends of the line sensor unit, two contact members that come into contact with the glass plate are formed. The scanning movement of the line sensor unit is accompanied by sliding of the contact members on a surface of the glass plate.
In a configuration of the scanner apparatus discussed in the Japanese Patent Application Laid-Open No. 2009-253327, a biasing force is applied to the vicinity of a center of the line sensor unit toward the glass plate. This creates a possibility that the line sensor unit may be warped with the two contact members (spacers) of both sides set as support points, and only the vicinity of the center may approach a surface of the glass plate, consequently shifting an in-focus position of a reading optical system from an upper surface of the glass plate. Then, an imaging failure (defocusing) occurs at the vicinity of the center, causing a read image to be blurred in a streaky shape.